There has been known a roadside object detection apparatus which detects height information on a road surface from camera images and detects a step on the road surface formed by roadside objects, such as a curb, from the height information (see Japanese Patent Application Publication No. 2014-002608).
The foregoing roadside object detection apparatus recognizes that there is a step when the amount of a height change of the road surface is larger than or equal to a threshold. In the case where the roadway has a gradient, the height of the road surface is different depending on the position of the roadway, so that the amount of a height change of the road surface cannot be detected accurately in some cases depending on how to set positions on the roadway.